The present invention relates to a protective agent for nervous system structural cells comprising a prostaglandin I derivative or a salt thereof as an active ingredient.
Recently, cases of various cerebrovascular diseases have increases with the arrival of an aging society. Cerebrovascular diseases are considered to be caused by aging, hypertension, arterial sclerosis, hyper lipidemia, and the like, and are generally called as stroke. Causal diseases of stroke include cerebral infarction (cerebral thrombosis and cerebral embolus), cerebral hemorrhage and subarachnoid hemorrhage, as well as transient cerebral ischemic attack, herpertensive encephalopathy, and the like. These causal diseases cause ischemia and damage or death of the structural cells of the nervous system around the ischemic area, resulting in occurrence of local mental and nervous diseases such as cerebrovascular dementia. Also, cases of Alzheimer diseases as representative presenile dementia have increased. Alzheimer diseases are representative diseases of presenile dementia, and cause memory disorder and spatial and temporal disorientation, and sometimes cause symptoms such as aphasia, apraxia, and agnosia. These symptoms are characterized by overall disorder of cerebral functions, and dementia is advanced in the final stage, resulting in death from systemic hyposthenia. Pathologically, it is known that Alzheimer diseases cause extensive encephalatrophy, Alzheimer""s neurofibrillary degeneration and senile plaque.
Although a cerebral circulation improving agent and a cerebral function improving agent have been used for improving psychoneurosis associated with cerebral nerve disorder and senile dementia, all medicines do not exhibit sufficient effect.
Peripheral nerve disorder is also called as multiple neuritis or neuritis, and occurs due to various causes such as heredity, trauma, intoxation, inflammation, metabolic disorder such as diabetic and the like, malignant tumors, peripheral nerve compression by a tumor, and the like. The symptoms of the peripheral nerve disorder include sensory disorder, motor disorder, hypomyotonia, areflexia, autonomic disorder, and the like, as well as showing a neurogentic pattern in an electromyogram and a decrease in peripheral nerve conduction velocity. Pathologic symptoms include nonspecific degeneration such as axonal degeneration, segmental demyelination, Waller degeneration, and the like. As a therapy, steroid, vitamin, an anti-inflammatory drug, an analgesic, and the like are used together with rehabilitation, but sufficient therapeutic effects cannot be obtained.
The above-described various diseases are due to a variety of causes, but various symptoms such as dementia as well as mental symptoms, sensory disorder, motor disorder, and autonomic disorder finally occur due to death, falling or functional disorder of the structural cells of the nervous system. Therefore, amelioration of disorder and improvement of these symptoms can be expected by strongly protecting the nerve cells. Furthermore, it has been made clear that nerve structural cells other than nerve cells, such as the above neuroglia and the like play a very important role in maintaining the function of the nerve cells, and amelioration of neuroglia disorder is effective in maintaining the function of the neuron.
Although prostaglandin derivatives are known to have various biological activities, they are classified in some groups according to modification of the 5-member ring comprising C-8 to C-12. Of these prostaglandin derivatives, compounds in which the carbon atoms at the 6- and 9-positions are combined through an oxygen atom are referred to as xe2x80x9cPGIxe2x80x9d, and prostaglandin I2 (PGI2, prostacyclin) is known as a representative. PGI2 is known as a substance having the action of suppressing platelet aggregation and the action of dilating peripheral vessels (refer to Nature, Vol. 268, p. 688, 1976).
As compounds in which instability of PGI2 is significantly improved, Japanese Examined Patent Publication Nos. 2-12226, 2-57548 and 1-53672 disclose PGI derivatives having a skeleton in which the structure of the exoenol ether moiety characteristic of the structure of PGI2 is converted into an inter-m-phenylene structure. Other known PGI derivatives include PGI derivatives in which the carbon atoms at the 6- and 9-positions are substituted by oxygen atoms, and PGI derivatives in which the oxygen atoms are substituted by carbon atoms or other hetero atoms. Examples of such derivatives include ataprost, ilopost, clinprost, ciprostene, naxaprostene, taprostene, cicaprost, pimilprost CH-169, and CS570 (refer to Gendai-Iryosha, xe2x80x9cGenerals of Prostaglandinxe2x80x9d No. 1, p. 123, 1994; New Drugs of Tomorrow, p. 15-IV-185, 1996; New Drugs of Tomorrow, p. 15-III-551, 1996). However, it is unknown that these prostaglandin I derivatives have the action of protecting the structural cells of the nervous system.
An object of the present invention is to provide a protective agent exhibiting the strong action of protecting the structural cells of the cerebral and peripheral nervous system, and the excellent effect of preventing or curing cerebrovascular disorder, cerebral nerve cell disorder, ischemic cerebral disorder, dementia, and peripheral nerve disorder due to diabetic or the like.
The present invention provides a protective agent for nervous system structural cells, comprising, as an active ingredient, a prostaglandin I derivative, preferably a prostaglandin I2 derivative.